As we cough, sneeze and sniff our way through the cold season, it may comfort us to know that technology has finally caught up with our expectations. Two new medicines promise to cure the common cold.
The drugs, one of which may be available within the next several months, stop cold viruses in their tracks, rather than just mask symptoms as current remedies do. Patients who have taken them report feeling better almost immediately, sleeping through the night and having to use fewer tissues on the cold’s hallmark runny nose. And one of the drugs also treats a handful of rare but often life-threatening ills such as chronic meningitis.
“These drugs are part of a revolution in the treatment of virally caused diseases,” said Catherine Laughlin, chief of virology at the National Institute of Allergies and Infectious Diseases in Bethesda, Md.
Researchers fighting cold viruses have benefited both from the massive research effort to combat AIDS, a viral disease caused by HIV, and the development of tools that allow them to peer deep inside a cell. With these advances, they’ve learned how to overcome two major hurdles in devising an effective cold medicine.
The first was that viruses are tough to hit with any accuracy because they insinuate themselves inside cells. In contrast, bacteria colonize in bodily fluids and cavities, making them easy pickings for antibiotics.
Added to this was the fact that there wasn’t just one kind of pesky microbe to keep at bay. A couple of different families of viruses, including rhinoviruses and coronaviruses, cause most colds.
And within these groups, more than 110 distinct rhinovirus types have been identified, and three or four coronaviruses infect humans.
“The challenge has been to find a single drug that would work against the different families of viruses as well as one that would precisely target the virus without hurting the cells,” Laughlin said.
Viruses are tiny capsules of protein that are much smaller than bacteria. The common analogy is that if a bacterium is equivalent to the size of a human, then a virus would be as large as an arm. Unlike almost any other living organism, viruses are incapable of reproducing themselves.
Instead, they must slither through a cell’s wall and commandeer the host’s genetic machinery, using it to churn out copies of themselves.
The two cold remedies now in the pipeline prevent this replication, thwarting the viruses without causing any apparent collateral damage in the host cells.
“Both of these drugs are very potent antiviral agents that work against a broad spectrum of different rhinoviruses,” said Dr. Ronald B. Turner, a professor of pediatrics at the University of Virginia in Charlottesville.
Each drug attacks the virus at a different stage of its life cycle but ends up with the same result: The virus can’t make copies of itself. One drug, called AG7088 for now because it’s in an early stage of development, is a protease inhibitor similar to the drugs that revolutionized AIDS treatment.
“The protease inhibitor halts the action of a key enzyme that the virus needs to replicate,” preventing the virus from squirting its genetic information into the cell’s DNA, Laughlin said. The medication has blocked enzyme activity in 100 strains of the cold virus, according to recent research.
The drug, a nasal spray that is inhaled several times daily, is made by Agouron Pharmaceuticals, a La Jolla, Calif., biotechnology company. It is in the middle of the second phase of human testing, according to an Agouron spokesman (new drugs normally go through three phases of human trials before being submitted for FDA approval).
Preliminary tests show that AG7088 reduces cold symptoms, while people who received a placebo experienced a full-blown cold.
Because the three phases of drug tests can be lengthy, AG7088 isn’t expected on the market for several years.
The other new medicine is Picovir, which is awaiting FDA approval and may be available in the local pharmacy within the next year.
Taken in a pill form, Picovir prevents the cold virus from entering the cell.
Scientists discovered this approach because of the development of an X-ray in the mid-1980s that had enough magnification to take detailed photographs of viruses. These X-rays revealed that picornaviruses, of which the cold-causing rhinoviruses are one, have a deep pocket or canyon that runs across the viral surface, or coat. Picovir wedges firmly inside this pocket, like a plug in a drain, and stops the virus from shedding its outer coating. If it can’t shed its coat, the virus can’t penetrate the cell membrane and infect the cell.
“We didn’t really know if blocking that one site would interfere with the life cycle of all these viruses,” said Mark McKinlay, vice president of research and development for ViroPharma, the Exton, Pa., company that makes Picovir. “But after much trial and error, we discovered a compound that locks tightly on to that site. The more tightly the drug binds, the greater the potency of the drug.”
In drug tests of more than 4,000 patients, people felt less miserable within 24 hours, and those who received the drug recovered a day sooner than the control group.
“The drug reduces viral shedding too,” McKinlay said, “which suggests that it cuts down the rate at which colds are spread.”
Picovir may prove most beneficial for people who are more vulnerable to a viral onslaught: the elderly, people with defective immune systems or those who suffer from ills such as asthma.
“The common cold can be fatal for someone whose immune system is compromised,” said Dr. Jose R. Romero, an associate professor of pediatrics at the University of Nebraska Medical Center in Omaha who has researched Picovir. “Rhinoviruses also trigger asthma, the No. 1 chronic illness in children. Preventive use might decrease the incidence of attacks.”
Still, there are a few drawbacks that may stand in the way of Picovir or AG7088 becoming true blockbusters. Though they reduce the severity and duration of cold symptoms — without the unpleasant side effects of current medications — they aren’t instant cures.
By the time you start feeling sick, you have been under siege for two to three days, which means the virus has established a firm toehold in the body. To get the maximum benefit from an antiviral medication such as Picovir, you need to get a prescription the minute you start feeling sick.
Another catch is that Picovir only foils the rhinovirus, which is responsible only for about half of all colds. If you’re attacked by another bug, it won’t help.
What’s more, the cold’s symptoms — the drippy nose, stuffed-up sinuses, cough, mild fever, sneezing, scratchy throat and headaches — are actually an inflammatory response, sparked by your immune system’s efforts to fight off the viral invaders.
Consequently, to get the kind of overnight relief we’ve gotten from antibiotics will require a one-two punch: an antiviral to stop the pathogens and an agent to quell the cascade of immune reactions.
